Purpose :
Based upon the location of local circumpapillary retinal nerve fiber layer (cpRNFL) thinning, [1] we hypothesize that the temporal halves of the superior and inferior quadrants of the disc are particularly vulnerable to early glaucomatous damage. Here we test this hypothesis.

Methods :
87 of 205 eyes with abnormal/anomalous discs, but with a mean deviation (MD) better than -6dB on 24-2 visual fields, were judged as glaucomatous by two experts based upon disc stereo-photos, 24-2 and 10-2 visual fields, an OCT summary report,[2] as well as information from the patients’ charts. The OCT summary report (Fig. 1) was based upon a swept source OCT wide-field cube scan (9x12 mm, DRI-OCT, Topcon, Inc). The region of the cpRNFL thickness plot falling into the red (1%) zone in Fig. 1A was considered abnormal, as were the regions of the RNFL (Fig. 1B) and retinal ganglion cell layer (Fig. 1C) appearing as red (1%) on the probability plots. The hypothesis is represented in Fig. 2, which shows the disc of a right eye with the superior (SVZ, orange) and inferior vulnerability zones (IVZ, green) indicated and the regions representing the macula shown in light blue and magenta. The macular vulnerability zone (MVZ) [3] is shown in black.

Results :
The example in Fig. 1 shows cpRNFL thinning (upper left panel A) that includes the IVZ (red arrow) and MVZ (black arrow). The damage to these regions is confirmed on the RNFL and RGC probability plots as indicated by the arrows. As predicted by the hypothesis, 84 (96.6%) of the 87 eyes, had damage in the SVZ (55, 63.2%), the IVZ (69, 79.3%) or both SVZ and IVZ (40, 46.0%). The remaining 3 eyes also had damage in the IVZ, although it was only borderline (yellow) on the cpRNFL plot. Damage to the macula was common (74 eyes, 85.1%), with damage to the inferior macula (62 eyes, 71.3%) more common than damage to the superior macula (41 eyes, 47.1%). Damage outside the macula was also common (84 eyes, 96.6%). Three eyes only had macular damage, while 13 eyes only had damage outside the macula.